Method of producing textile reinforced thermoplastic or thermoset pipes utilizing modified dorn structures

ABSTRACT

Novel thermoplastic pipes which can withstand extremely high internally generated and/or applied pressures for utilization within, primarily, high pressure underground liquid and gas transport systems are provided. Such pipes are improvements over standard metal (i.e., steel, lead, and the like) pipes due to construction costs, shipping costs, implementation costs (particularly underground), modulus strength allowances to compensate for underground movements (i.e., earthquakes and tremors), non-rusting characteristics, and ease in manufacture. Such pipes are preferably reinforced with specific fabric articles which permit a lower thickness of plastic to be utilized than is generally required to withstand high pressure situations. A simplified, potentially on-site production method for producing more uniform, better-performing pipes as well as a specific molding dorn for such a purpose are also contemplated within this invention.

FIELD OF THE INVENTION

[0001] The present invention generally relates to novel thermoplasticpipes which can withstand a varied range of internally generated and/orapplied pressures for utilization within, primarily, underground liquidand gas transport systems. Such pipes are improvements over standardmetal (i.e., steel, lead, and the like) pipes due to construction costs,shipping costs, implementation costs (particularly underground), modulusstrength allowances to compensate for underground movements (i.e.,earthquakes and tremors), non-rusting characteristics, and ease inmanufacture. Such pipes are preferably reinforced with specific fabricarticles that permit a lower thickness of plastic to be utilized than isgenerally required to withstand high pressure situations. A simplified,potentially on-site production method for producing more uniform,better-performing pipes as well as a specific molding dorn for such apurpose are also contemplated within this invention.

BACKGROUND OF THE INVENTION

[0002] Underground transport of liquids and gases has been utilized formany years. Such underground transport has proven to be the mostefficient and safest manner in which to transport potentially explosive,flammable, and/or toxic liquids (such as crude oil, for example) andgases (such as methane and propane, as examples) long distances. Theprinciple method followed to provide such long distance undergroundtransport has been through metal tubes and pipes. In the past, theutilization of metals (such as steel, copper, lead, and the like) waseffective from cost and raw material supply perspectives. However, withthe population growing throughout the world and the necessity fortransporting liquids and gases to more remote locations increases, thecontinued utilization of such metal articles has become more and moredifficult for a number of reasons. Initially, the production of suchmetal tubes and pipes must be undertaken through high-temperatureproduction methods at specific foundries which are normally located asubstantial distance from the desired installation site. Such off-siteproduction thus requires transport of cumbersome metal articles to theinstallation location and then subsequent placement into already-dugchannels. These procedures are, again, difficult to follow since metalarticles are rather heavy and must be connected together to form thedesired pipeline. Additionally, in order to reduce the number ofconnections between individual pipes, longer metal pipes could beformed, which adds to the complexity with an increase in required weldedconnections. Further problems associated with metal pipes and tubesinclude, without limitation, the potential for rusting (which maycontaminate the transported liquid or gas), the low threshold ofearth-shifting which could cause a break within the pipeline, and thedifficulty in replacing worn out metal pipes in sections, again due tothe metal pipe weight, metal pipe length, and connection welds. Thesebreak problems have proven to be extremely troublesome in certaingeographic areas which are susceptible to earthquakes and tremors on aregular basis. When such unexpected quakes have occurred in the past,the metal gas and liquid pipelines have not proven to be flexible enoughto withstand the shear forces applied thereto and explosions, leaks, ordiscontinued supplies to such areas have resulted. These metal articleshave remained in use because of their ability to withstand highpressures. Furthermore, although such metal pipes are designed towithstand such high pressures (i.e., above 80 bars, for instance), oncea crack develops within the actual metal pipe structure, it has beenfound that such cracks easily propagate and spread in size and possiblynumber upon the application of continued high pressure to the sameweakened area. In such an instance, failure of the pipe is thereforeimminent unless closure is effectuated and repairs or replacements areundertaken.

[0003] Although there is a need to produce new pipelines to remotelocations around the world, there is also a need to replace thenow-deteriorating pipelines already in use. Aging pipelines haverecently caused great concern as to the safety of utilizing such oldarticles. Unexpected explosions have occurred with tragic consequences.Thorough review and replacement of such old metal pipes is thusnecessary; however, due to the difficulties in determining the exactsections of such pipelines which require replacement, there is a desireto completely replace old pipelines but following the same exact routes.Again, due to the difficulties noted above, there is a perceived need todevelop more reasonable, safer, longer-lasting, easier-to-install,non-rusting, non-crack propagating, and more flexible pipelinematerials. To date, there have been some new thermoset or thermoplasticarticles which are designed to withstand rather low pressureapplications (i.e., 20 bars or below) and which include certainfiber-wound reinforcement materials (including fiberglass, polyaramids,polyesters, polyamides, carbon fibers, and the like). However, theresultant articles do not include specific textile reinforcements (theyare fibers wound around specific layers of plastic material) and thusare difficult and rather costly to produce. Furthermore, suchfiber-wound materials cannot be easily produced at the pipe installationsite again due to the complexity of creating fiber-wound reinforcementarticles subsequent to thermoplastic or thermoset layer production.Additionally, with such off-site production, transport and in-groundplacement remain a difficult problem. Thus, although some improvementshave been provided in the past in relation and in comparison to metalpipes and tubes, there simply is no viable alternative presented to datewithin the pertinent prior art which accords the underground liquid andgas transport industry a manner of replacing such high pressure metalarticles.

[0004] Additionally, prior attempts at producing reinforced resinouspipes have uncovered other problems with such final products, mostnotably non-uniformity in both the thickness of the pipe walls as wellas the shape of the pipe itself. With such non-uniformity, limitationsas to pressure resistance may occur, particularly due to the weakeningof discrete areas of the pipe to a greater degree than the other areasof the same article. In such a situation, even with reinforcementspresent to provide greater elongation at break for the entire article,there still exists a potential problem with greater stress being placedon the weakest portion of the pipe upon exposure to higher pressures.Thus, a procedure to produce a more uniform thermoplastic, preferablyreinforced, pipe article is necessary to provide greater security andmore reliable pipes over the lifetime of use of such an article. Sincesuch thermoplastic or thermoset articles do not return to their originalshape and/or thickness after pressure stresses have thinned the wallsthrough expansion, again, there is a great need to produce a moreuniform article to defend against uneven thinning.

[0005] Furthermore, upon utilization of reinforcements, such as withoutlimitation, fiber-wound tapes (such as polyaramids, and the like),textile layers (including, scrim, non-woven, woven, and the likefabrics) in-laid or surrounding at least one layer of resinous material,and the like, it is imperative that effective adhesion be effectuatedbetween the resinous layer and the reinforcement material. In the past,wrapping of fiber-wound material around the target resin has beenpracticed with the possible inclusion of an adhesion promoterformulation to aid in adhesive effects. Also, since such wrapping mustbe performed on molten resin to achieve sufficient adhesivecharacteristics, the cooled resin thus adheres more readily to thealready-in-place reinforcement material. However, even with such aprocedure, there is no specific guarantee that appreciable amounts ofmolten resin will effectively enter the interstices of the particularwrapped tape material. Thus, a more reliable method is necessary toprovide better adhesion between resin and reinforcement material. Anymethod of providing this benefit as well as the aforementioned greateruniformity in shape and wall thickness is thus of great importance tothe resin pipe article industry. Unfortunately, to date, no such methodhas been provided, taught, or even mentioned within the pertinent priorart or anywhere within the industry.

OBJECTS OF THE INVENTION

[0006] It is thus an object of this invention to provide such a viablealternative method for replacing or overcoming the shortcomings anddifficulties of high pressure (i.e., from about 20 to about 100 bars)underground metal pipes and tubes. Another object of this invention isto provide a suitable fabric reinforcement system which permits arelatively low amount of thermoplastic or thermoset composition to beutilized in order to produce a pressure-resistant thermoplastic pipearticle. Yet another object of this invention is to provide aninterlocking mechanism to best ensure the textile reinforcement layerremains in place during and after introduction of the outerthermoplastic or thermoset layer. Still another object of this inventionis to provide a suitable simplified method of producing a resinous pipearticle of substantial uniformity in wall thickness and shape as wellas, if such article includes a reinforcement material, greater degreesof adhesion between the resin component and reinforcement component ofsuch pipes. Also, another object is to provide a novel dorn article forthe purpose of initially applying reinforcement material to resincomponent which then cools as the combined materials move along the dornto form the aforementioned uniform and greatly adhered together article.Alternatively, the dorn may be utilized on a resin component alone toprovide a uniform shape and/or wall thickness for the resultant pipe, ifdesired.

SUMMARY AND BRIEF DESCRIPTION OF THE INVENTION

[0007] Accordingly, this invention encompasses a method of producing aresinous pipe comprising at least one layer of thermally manipulatedpolymeric material, wherein said polymeric material is first heated andapplied around a first end of a molding dorn having a first end and asecond end as well as areas in between, and subsequently moved along thelength of said dorn to said second end of said dorn and eventuallycooled, wherein said dorn exhibits the shape diameter throughout itsentire structure, but exhibits a greater surface area at said first endthan at said second end. Preferably, said dorn also exhibits a reductionin surface area numerically from said first end through all areas inbetween said first end to second end and ultimately to said second end.Preferably, said second end is perfectly round in shape. Clearly, if thefirst end of the dorn must have a greater surface area (with the samediameter as the second end), then it must exhibit a roughened surfaceor, at least, indentations throughout. The term “diameter” in such aninstance is intended, for the first end, to indicate the greatestdistance from the greatest extension of the surface (at its greatestmeasure from the middle of the dorn to the surface exactly opposite. Inorder to provide the desired uniformity of shape and wall thickness,such diameter must be the same as that of the second end (which shouldbe substantially round, as noted above). Without such a specificdiameter, such uniformity would not be possible, as the walls would notremain at the same thickness at all points on the dorn. Moreimportantly, however, once the resin is applied around the dorn itself,if the overall diameter of the dorn is altered, the resultant moldedpipe will exhibit the aforementioned problems of non-uniform wallthickness or uneven shape. The pipe made therefrom said method andtherewith said dorn comprises at least one layer of textilereinforcement material, adhered to at least one thermally manipulatedpolymeric material or, preferably such textile reinforcement material issandwiched between at least two distinct layers of such thermallymanipulated polymeric material, wherein the elongation at breakexhibited by such a pipe is limited solely to the elongation at breakexhibited by said textile reinforcement material, and wherein saidtextile reinforcement material exhibits an elongation at break of atmost 50%, preferably at most 30%, more preferably at most 20%, stillmore preferably at most about 15%, even more preferably at most about10%, and most preferably at most 6%. Preferably said pipe is constructedto withstand at least 100 bars of internal pressure before exceeding theelongation at break limit. An alternative yet also preferred embodimentis a pipe which exhibits at most 20 bars of pressure of internalpressure before exceeding the, elongation at break limit.and a wallthickness of said polymeric material of at most {fraction (1/15)}th ofthe diameter of said pipe, preferably at most about {fraction(1/25)}^(th,) more preferably at most about {fraction (1/50)}, and mostpreferably at most about {fraction (1/100)}th. Such pipes thus exhibitwall thicknesses of from about 0.5 millimeter to about 20 millimeters(and potentially thicker, if desired). Also contemplated within thisinvention is the pipe as noted above wherein the textile reinforcementmaterial introduced within said pipe is a flat structure having a firstside and a second side which is formed into a tubular structure aroundthe inner polymeric layer upon overlapping contact of said first andsecond sides and which possesses means to adhere or interlock saidoverlapped first and second sides.

[0008] The term “thermally manipulated polymeric material” is intendedto encompass the well known polymeric compositions of a) thermoplasticsand b) thermosets. Such terms are well known and describe a) anysynthetic polymeric material that exhibits a modification in physicalstate from solid to liquid upon exposure to sufficiently hightemperatures and b) any synthetic polymeric material that exhibitsorientation in a preselected configuration upon exposure to sufficientlyhigh temperatures. Most notable of the preferred thermoplastic types ofmaterials are polyolefins (i.e., polypropylene, polyethylene, and thelike), polyester (i.e., polyethylene terephthalate, and the like),polyamides (i.e., nylon-1,1, nylon-1,2, nylon-6 or nylon-6,6), andpolyvinyl halides (i.e., polyvinyl chloride and polyvinvyl difluoride,as merely examples). Preferred within this invention are polyolefins,and most preferred is polypropylene. Such materials are generallypetroleum byproducts and are readily available worldwide. Thesematerials are produced through the polymerization of similar ordifferent monomers followed by the melt extrusion of the polymerizedmaterials in pellet form into the desired shape or configuration. Uponsolidification through cooling, such materials exhibit extremely highpressure resistance, particularly upon introduction of nucleatingagents, such as substituted or unsubstituted dibenzylidene sorbitols,available from Milliken & Company under the tradename Millad®, and/orcertain sodium organic salts, available form Asahi Denka under thetradename NA-11™. Such nucleating agents are either mixed and providedwithin the pelletized polymers, or admixed within the melted polymercomposition prior to extrusion. These compounds provide strengthenhancements and accelerate thermoplastic production by producingcrystalline networks within the final thermoplastic product upon coolingat relatively high temperatures. Theoretically, at least, with astronger initial thermoplastic product, the more durable and potentiallylonger functional lifetime provided by such a product. Preferredthermoset materials include materials such as polyurethane,polycarbonate, or the like.

[0009] Since pipe diameters utilized for largescale undergroundtransport applications are generally measured in feet rather than inchesor millimeters, the wall thicknesses required to provide the desiredhigh pressure characteristics are extremely high for thermoplastics orthermosets alone. Although such thermoplastic and/or thermoset materialsprovide certain pressure resistances, in general the wall thicknessrequired to withstand pressures of about 80 bars requires a standarddiameter to wall thickness ratio of at most 11:1 (for polyethylene forexample). Thus, in order to provide such high pressure characteristicswithout exceeding the elongation at break limits of the polymericmaterials present in pipe form (i.e, substantially cylindrical), withpipe diameter of, for example, about 232 millimeters (about 9 inches),the wall thickness of the pipe must be at least about 21 millimeters, orabout 0.85 inches) to withstand such high pressures. Even with suchthick walls, the polymeric materials would not provide any resistance tocrack propagation should a weakened area of the pipe produce such aburst point. There is a strong desire to increase the pressureresistance (and thus consequently, the elongation at breakcharacterstics) of the target polymeric pipe material in order either toprovide much thinner wall thicknesses without a loss in pressureresistance as compared with the standard polymeric materials alone, orto provide greater pressure resistant thick-walled pipes which are morereliable upon exposure to very high pressure situations. Such desirablebenefits have been unavailable through practice of a relatively simplemanufacturing method with actual textile reinforcement materialsproviding the basis of pressure resistance for the entire pipe article.

[0010] Apparently, upon application of internal pressure within suchnon-reinforced thermoplastic and/or thermoset piping materials, thematerials expand in the direction dictated by the pressure thereforethinning the wall thickness either to the point of breaking (i.e., tothe elongation at break limit) or until the pressure is discontinued.After discontinuing the pressure, however, the pipe walls do not returnto their original thicknesses. Also, if the pressure is appliedunevenly, or if there is a discrete area within the thermoplastic orthermoset pipe wall which is already thinner than the other areas, thenthe pipe will more easily burst in relation to the pressure buildup orin relation to the thinner wall portion. In order to alleviate suchdetrimental expansion and burst possibilities within thermoplasticpiping materials, reinforcing materials have been developed tocompensate for such problems. However, in the past, such pipingmaterials have been limited primarily to hoses and short tubes (i.e.,automobile tubing) which did not require the ability to withstandextremely high pressures.

[0011] It has now been found that the incorporation of certain textilereinforcement materials permit reduction of the diameter to wallthickness ratio for standard thermoplastic and/or thermoset materials byat least a factor of 1.5 (a ratio for any thermoplastic of at the most1:17 in order to withstand a pressure of at least 80 bars). Preferably,then , the thickness of the inventive pipe walls should be no greaterthan about {fraction (1/17)}^(th) of the pipe diameter; more preferablyno more than about {fraction (1/20)}^(th,) and most preferably nogreater than about {fraction (1/25)}^(th) of the pipe diameter. The term“withstand pressure” is intended to encompass the ability to preventelongation of the entire pipe material to a point of breaking orweakening in discrete areas (i.e., thinning of certain areas to permitleakage). Such ability to withstand pressure is imperative since theutilization of high pressures internally provides a consistent andcontinuous force seeking equilibrium with the external pressures. Anyexcess thinning of the pipe material would therefore most likely resultin bursting of the pipe due to physical requirements of equalingpressures. Such textile reinforcement materials thus aid in thereduction of elongation of the thermoplastic or thermoset pipecomponents upon application of high pressures therein. As notedpreviously, it has been determined that the elongation at break of suchtextile reinforcements provides the overall elongation at breakexhibited by the target pipe article, particularly upon the presence ofsuch reinforcement materials between at least two distinct layers ofthermoplastic or thermoset materials. In such a manner, the entirearticle relies primarily upon at least one textile reinforcement layerto provide the desired high elongation at break limit and the low crackpropagation exhibited by the reinforced thermoplastic or thermosetmaterial. Furthermore, such a reinforcement material also aids inproviding an increased tear resistance to the overall pipe article whichaids in reducing the chances of a breach in structural integrity as aresult of external shear force application (i.e., earth tremors, and thelike). Since there is strict reliance upon such properties exhibited andprovided by the textile reinforcement layer, the amount of thermoplasticor thermoset materials can be substantially reduced with no reduction inreliability under pressurized situations. Also, if so desired, the usermay still utilize a substantial amount of thermoplastic or thermosetmaterial in combination with the sandwiched textile reinforcement layeror layers with confidence that, again, the inventive pipe article willexhibit improved and reliable pressure resistance, crack propagationresistance, and tear resistance.

[0012] Of enormous importance in this instance is the flexibilityexhibited by the inventive pipes when subjected to external shearforces, for example earth tremors, and the like. Such flexibilitypermits the pipes to exhibit some movement in relation to the shearforces generated by such external occurrences. In the past, as notedabove, metal pipes suffered from the lack of flexibility in that theapplication of such external shear forces would result in the burst ofcertain pipes due to such external forces exceeding the shear forcethreshold possessed by the metal materials. Such flexibility is mostsuitably measured in terms of tear resistance to the overall pipearticle. In general, metal pipes exhibit at most a tear resistance ofabout 6% (copper exhibits the highest such tear resistance), which isextremely low when the potential for very strong shear forcesunderground are significant (particularly in certain parts of the worldprone to earth tremors, earthquakes, and the like). The thermoplasticsand/or thermosets provide initial tear resistance measurements in excessof at least 20%, with a potential high measurement of more than about100%, particularly upon incorporation of the sandwiched textilereinforcement material as discussed above. Thus, the inventive pipesshould be able to withstand enormous shear forces, at least better thanmetal pipes, due to their exhibited tear resistance and thus flexibilitycharacteristics.

[0013] As noted above, preferably at least two layers of suchthermoplastic and/or thermoset materials are present within theinventive thermoplastic and/or thermoset pipes. These layers areseparated, at least in part, by a textile reinforcement material. Thetotal wall thickness of the inventive pipe, as noted above, is dependentupon the discretion of the producer and in relation to the propertiesprovided by the textile reinforcement layer itself. If a thin-walled,low pressure pipe is desired, then the typical wall thickness may beanywhere from about 4 to about 15 millimeters. A higher elongation atbreak characteristic exhibited by the textile reinforcement permitslower thicknesses to be utilized. Such elongation at breakcharacteristics are generally measured by the amount of force suchtextile reinforcements may withstand. Thus, a textile exhibiting atleast an elongation at break of about 2-3% (i.e., similar to thatexhibited by steel but greater than for most thermoplastic and/orthermoset compositions) is desired. Of course, textile materialsexhibiting far in excess of this elongation at break minimum are morepreferred, with no real maximum level, only that which may deleteriouslyaffect the overall stiffness of the product, thereby potentiallyproviding tear resistance problems. The elongation at break level forpreferred textile reinforcements is determined by a number of factors,including the tenacity of the constituent fibers within the textile (ahigher dtex provides a stronger textile overall), the angle of contactinrelation to the direction of the pipe (angles of form 40 to 70° arepreferred, while specific angles of between 45 and 65° and 50 and 55°are more preferred, respectively. An angle of specifically 54° 44′ hasbeen found to provide the greatest overall strength to the target pipearticle. Thicker layers of textile reinforcement material also appear toprovide stronger overall products, as do scrim and in-laid textiles.

[0014] The term “textile reinforcement material” or “textilereinforcement” or “textile reinforcement layer” simply requires acombination of individual yarns or fibers in a configuration which is anintegrated two-dimensional article prior to incorporation between the atleast two layers of thermally manipulated polymeric materials. Thus,wound strips incorporated over a completed inner layer is notencompassed within such a definition. Nor are fiber-containing tapearticles which are also wound around a formed polymeric pipe article.The specific textile reinforcement materials may be of any particularconfiguration, shape, and composition. The inventive textilereinforcements are present as at least a single layer of material with atotal aggregate thickness of at least about 500 microns, preferably atleast about 400 microns, more preferably at least about 300, and mostpreferably up to about 300 microns. Such textiles preferably exhibit amesh structure between the two layers of thermoplastic and/or thermosetmaterials. In general, it is highly desired that synthetic fibers,either alone, or in conjunction with metal threads, be utilized withinthe reinforcement materials. Such synthetics are less likely to besusceptible to deterioration over time due to potential presence ofbacteria, moisture, salts, and the like, within and around the pipes asthey would be positioned underground. However, with the properprecautions of proper coating, finishing, and the like, natural fibersmay serve this purpose as well. The preferred textile reinforcements maybe knit, scrim, woven, non-woven, in-laid, and the like, in form, withscrim and in-laid textiles most preferred. Such forms are most easilyproduced and maneuvered during the actual pipe production procedure.With in-laid textiles, at least two layers are desired to have one layeroriented at one angle and the other its complement in relation to thedirection of the target thermoplastic pipe. Thus, one layer would beplaced with all yarns and/or fibers oriented at an angle of about 54°44′ to the pipe direction, the other oriented at an angle of about −54°44′. In order to more easily hold such in-laid fabric layers in place, athermoplastic film may be applied either between or on top of one orboth layers. Such a film is preferably extremely thin (i.e., less thanabout 200 microns, preferably less than 100 microns, and most preferablyless than about 50 microns) and, being a thermoplastic, will easilyreact with the outer layer of thermoplastic upon heating and moldingaround the inner layer/fabric reinforcement composite. Alternatively,sewn threads may be utilized to hold such multiple layers in place priorto, during, and after pipe production. Although it is preferred thatsuch textile reinforcement material is utilized within the inventivemethod, as noted previously, such material may be omitted if very lowpressures are desired of the end pipe product. Also, fiber-woundwrapping (i.e., tapes) may also be utilized for such purpose within theinventive method (as well as any other reinforcement means which adhereseasily and sufficiently to the resin components of the target pipearticle).

[0015] The yarns within the specific textile reinforcement materials maybe either of multifilament or monofilament and preferably possess arelatively high dtex, again, to provide the desired tenacity andstrength to the overall pipe article. A range of decitex of from about200 to about 24,000 is therefore acceptable. Mixtures of such individualfibers may be utilized as well as long as the elongation at break of thecomplete textile reinforcement material dictates the elongation at breakfor the complete thermoplastic and/or thermoset article. Multifilamentfibers are preferred since they provides better adhesive properties andgreater overall strength to the textile. The individual fibers may be ofpolyester, polyamide, polyaramid, polyimide, carbon, fiberglass(silicon-based, for example), boron-derivative, and possibly,polyolefin, in nature. Again, natural fibers, such as cotton, wool,hemp, and the like, may be utilized but are not as trustworthy as thesynthetitic types listed above. Due to high processing temperaturesassociated with polymeric pipe extruding, it is highly desirable toavoid the sole utilization of low melting-point polyolefin yarns.However, a plurality of individual fibers of such polyolefins (i.e.,polypropylene, polyethylene, and the like) may be utilized incombination with the other synthetic fibers in order to improve adhesionupon melting of such yarns upon exposure to the higher temperaturespresent during the contacting of the textile reinforcement to thethermoplastic and/or thermoset inner and outer layers. Fiberglass andboron-derivatives are preferred due to their strength characteristicsand their alkaline resistance. The remaining fibers are also acceptable,including, most prominently, polyaramids, polyimides, carbon fibers, andpolyesters. Polyesters are desirable from a cost standpoint while theremaining fibers are excellent with regards to strength.

[0016] Of particular preference within this invention are yarns ofcore-sheath types, as taught within U.S. Pat. No. 5,691,030 to DeMeyer,herein entirely incorporated by reference. Such specific yarns permitbreakage of the sheath components without affecting the strength of thecore filaments therein. Such core filaments may be monofilamentsynthetic fibers (such as polyester, polyamides, polyaramids,polyolefins, and the like), although, in one potentially preferredembodiment, at least a portion of such core filaments are metallic innature (such as, preferably, copper, silver, gold, and the like) inorder to permit conduction of electrical current and/or heat over theentire pipeline. Such metal threads, fibers, yarns, etc., are notlimited to being core filaments and thus may be present as distinctin-laid, woven, knit, no-woven, placed, scrim, components.

[0017] Such metallic components provide great strength as needed withinthe fabric reinforcement materials; however, they also may serve toprovide other highly desirable benefits for both the inventive pipes andthe overall pipeline comprising such pipes. For example, such conductivecomponents may permit the introduction of a low electrical current overthe entire pipeline (through a continuous connection of metalcomponents) or through certain segments thereof. In such a manner, adetection system may be implemented to determine where and at what timea pipe has burst or a leak is present. Upon interruption of the desiredelectrical signal (i.e., the specific amps of current), a valve may beoperated to close off a certain portion of the pipeline until repairsare made. Such a system merely requires the connection of an ampmeter tothe pipeline and integration of a valve in relation to the measuredamperage flowing through the pipeline itself. Furthermore, with such adetection system, the ability to detect such problems from above-groundwould be provided as well as a signal in relation to a low amperagecount can be produced thereby signifying the specific location of theproblem. Such a method thus facilitates detection and replacement ofsuch thermoplastic pipes.

[0018] Additionally, in certain locations freezing temperatures mayprovide difficulty in transporting certain gases and liquids undergroundwithout the ability to provide heated pipes. The presence of metalyarns, etc., facilitates the generation of heat, potentially, within thedesired pipes with, again, the introduction of certain selected amountsof current and/or heat over the metal components. The heat generatedthereby may be utilized to effectively keep the desired pipes fromfreezing thereby permitting continuous transport therethrough.

[0019] Even upon utilization of a fabric reinforcement materialconfigured at the preferred angles noted above in relation to the pipedirection (i.e., 40 to 70°, most preferably 55°), the addition of across-yarn within each repeating design, stitch, pattern, etc.,configured at an angle of 0° in relation to the pipe direction is highlydesired. Such a cross-yarn permits melting of the entire pipe structureat discrete places in order to allow for curvatures to be introducedwithin the pipeline without deleteriously affecting the strength of theremaining fabric reinforcement material or compromising the shearstrength of the entire pipe composite, particularly at the specific bentplace. Such an improvement again shows the benefits of thermoplastichighi pressure pipes since such curvatures may be produced at any angleand on-site on an as needed basis. Historically utilized metal pipesrequired formation of necessary curvatures at the foundry; if the angleof curvature was incorrect, new parts had to be produced to compensatefor such a mistake. The inventive pipes permit on-site corrections ifnecessary.

[0020] It is desirable that the fabric reinforcement materials are inmesh form and thus exhibit open spaces between the constituent fibersand/or yarns therein. Such open space should be large enough to permit aportion of the heated liquid outer thermoplastic layer to adhere to thealready formed inner thermoplastic layer therethrough and after coolingof the outer layer. In such a manner, not only is the three layer pipestronger, the reinforcement materials are better held in place. Althoughlarger open spaces between constituent fibers and/or yarns arepreferred, the only requirement is that at least a portion of the outerlayer exhibit some ability to adhere with the surface of the inner layerin contact with the fabric reinforcement materials. Thus, a range ofpreferred open space between individual constituent yarns of an area aslow as 0.001 square millimeters and as high as about 1 square centimeteris desired.

[0021] The separate polymeric material layers and textile reinforcementlayer may comprise any number of additives for standard purposes, suchas antimicrobial agents, colorants, antistatic compounds, and the like.Such antimicrobial agents would potentially protect the inner liningfrom colonization of unwanted and potentially dangerous bacteria (whichcould potentially create greater pressure within the pipes if a propernutrition source is present). Preferably, such an antimicrobial agentwould be inorganic in nature and relatively easy to introduce within thethermoplastic compositions within the pipe. Thus, silver-basedion-exchange compounds (such as ALPHASAN®, available from Milliken &Company, and other types, such as silver zeolites, and the like) arepreferred for this purpose. Colorants may be utilized to easilydistinguish the thermoplastic layers for identification purposes. Anypigment, polymeric colorant, dye, or dyestuff which is normally utilizedfor such a purpose may be utilized in this respect for this invention.Antistatic compounds, such as quaternary ammonium compounds, and thelike, permit static charge dissipation within the desired thermoplasticmaterials in order to reduce the chances of instantaneous sparkproduction which could theoretically ignite certain transported gasesand/or liquids. Although the chances of such spark ignition areextremely low, such an additive may be necessary to aid in this respect.

[0022] Such fabric reinforcement materials provide the aforementionedresistance to expansion, swelling, and/or burst due to the applicationof extremely high internal pressures within the target thermoplasticpipe material. Preferably, the fabric reinforcement material isconfigured at an angle of about 55° (54°44′) in relation to thedirection of the target pipe itself. In such a manner, the fabricprovides the best overall strength and thus resistance to internalpressures due to its resistance to shear forces generated by theinternal pressure within the pipe. Depending on the amount of fabricutilized, however, the angle of contact may be as low as 0° and as highas 90°. With an angle configured in the same direction as the pipeitself, there is a higher risk of pipe burst due to the low shear forcethreshold provided by the fabric. Thicker fabrics may compensate forsuch shear force problems; however, the actual angle of contact shouldbe from about 40 to about 70°, with the particular 54° 44′ angle mostpreferred. Furthermore, the number of fabric layers utilized may beplural to provide greater reinforcement strength. In such an instance,it is highly desirable that contacting layers of fabrics be configuredat opposite angles of contact in relation to the pipe direction toaccord, again, the strongest reinforcement possible. The utilization ofa supplemental textile reinforcement layer oriented at an angle ofcontact with the pipe direction of either 0 or 90° imparts certaindesirable properties to the overall pipe article. Most notably, crushresistance is provided to ready-made pipes which are necessarily woundon a creel for transport to an installation site. A 0° reinforcementangle provides the best stiffness to compensate for the weight generatedby rolled pipes. Also, should an initial production of the inner layerbe desired in roll form, the incorporation of such a 0° textilereinforcement component may alleviate crushing problems associated withsuch storage and transport. A 90° orientation improves upon the tearresistance of the final product.

[0023] Although only two specific layers of thermoplastic and/orthermoset materials are required, it is to be understood that more thantwo such layers are acceptable within this invention. Such additionallayers may be of any type (and not necessarily thermoplastic and/orthermoset), including, without limitaition, metal, ceramic, glass-filledplastic, rubber, and the like.

[0024] Other alternatives to this inventive article will be apparentupon review of the preferred embodiments within the drawings asdiscussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings, where:

[0026]FIG. 1 shows an embodiment of the present invention illustrated asthe pipe 10;

[0027]FIG. 2 shows a cross-section of the pipe 10 from FIG. 1;

[0028]FIG. 3 shows a partial cross-sectional view of an apparatus forforming the pipe from FIG. 1;

[0029] FIGS. 4A-H illustrate cross-sectional views of the apparatus andpipe from FIG. 3, illustrating the method of joining a reinforcingfabric with an inner wall;

[0030]FIG. 5 illustrates a partial view of a textile for use in formingthe pipe from FIG. 1 with the apparatus in FIG. 3;

[0031]FIG. 6 illustrates a textile for use as the reinforcing fabric forforming the pipe from FIG. 1 with the apparatus in FIG. 3; and

[0032]FIG. 7 illustrates an apparatus for the in situ formation andplacement of the pipe from FIG. 1.

[0033]FIG. 8 illustrates a cross-sectional view of another preferredembodiment of a pipe showing the utilization of multiple textilereinforcement components connected by tapered ends and placed around thecircumference of the resin material.

[0034]FIG. 9 illustrates the inventive molding dorn in cross-section atits first end (of high surface area) utilized within the inventivemethod of producing resin pipes.

[0035]FIG. 10 illustrates the inventive molding dom in cross-section atits second end (of low, smooth surface area) utilized within theinventive method of producing resin pipes.

[0036]FIG. 11 illustrates a side view of the inventive molding dorn.

[0037]FIG. 12 illustrates the inventive molding in cross-section at itsfirst end with the resin and textile reinforcement thereto applied atits initial stage of molding.

[0038]FIG. 13 illustrates the inventive molding in cross-section at itssecond end with the resin and textile reinforcement thereto applied andadhered together at its final stage of molding.

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] Reference will now be made in detail to potentially preferredembodiments of the invention, examples of which have been illustrated inthe accompanying drawings. It is to be understood that these are in noway intended to limit the invention to such illustrated and describedembodiments. On the contrary, it is intended to cover all alternatives,modifications and equivalents as may be included within the true spiritand scope of the invention as defined by the appended claims andequivalents thereto.

[0040] Referring now to the figures, and in particular to FIGS. 1 and 2,there is shown a pipe 10 illustrating one embodiment of the presentinvention. The pipe 10 generally includes an inner wall 110, areinforcing textile 120, and an outer wall 130. The inner wall 110 ispreferably formed of a thermoplastic material, and has an inner passagesurface 111 and an inner wall textile interface zone 113. The innerpassage surface 111 defines the interior of the pipe 10. The outer wall130 is preferably formed of a thermoplastic material, and has an outersurface 133 and an outer wall textile interface zone 131. Thereinforcing textile 120 wraps around the inner wall 110 and engages theinner wall textile interface surface 133. The reinforcing textile 120has a sufficient width to surround the inner wall 110, and have textileoverlap sections 121 where the edges of the reinforcing material overlaparound the inner wall 110. A textile locking system 123 is employedbetween the textile overlap sections 121 to prevent the ends of thereinforcing material 120 from separating. The outer wall textileinterface surface 131 engages the reinforcing textile 120 and the outerwall surrounds the reinforcing textile 120. Such a textile lockingsystem 123 may alternatively comprise an adhesive composition (such as,as merely example, heat-activated or pressure-activated adhesives) whichpermits a secure, long-term connection between the overlap sections 121and thus prevents separation of the two sections upon pipe productionand potential elongation caused by high internal pressures.

[0041] Referring now to FIG. 3, there is shown a cross section of anapparatus 200 for forming the pipe 10 in FIGS. 1 and 2. The apparatus200 generally includes an inner wall die 210, a mandrel 220, areinforcing textile guide 230, and an outer wall die 240. The inner walldie 210 has an inner wall die aperture 211. The mandrel 220 extendsthrough the inner wall die aperture 211 and includes an outer surface221 for forming the inner passage 111 of the pipe 10 and providingsupport to the inner wall 110 during the formation of the pipe 10.

[0042] Still referring to FIG. 3, the reinforcing textile guide 230 ispositioned around the mandrel 220 after the inner wall die 210. Thereinforcing textile guide 230 includes an inside textile guide 231 andan outside textile guide 232 for guiding the edges of the reinforcingtextile 120 to position the reinforcing textile 120 around the innerwall 110. In one embodiment of the apparatus 200, the reinforcingtextile guide 230 includes a joint material injector 235 that is locatedto insert a material between the overlap textile sections 121. In yetanother preferred embodiment, the reinforcing textile guide 230 includesa closing roller 237 that presses the overlapping portions of thereinforcing textile 120 together.

[0043] Referring still to FIG. 3, the outer wall die 240 is locatedaround the mandrel 220 and includes an inside die wall 241 and anoutside die wall 245. The inside die wall 241 of the outer wall die 240includes an inside die wall aperture 242 to receive the inner wall 110and reinforcing textile 120 combination. The inside die wall aperture242 has an inside die wall aperture taper 243 for assisting the innerwall 110 and reinforcing textile 120 combination to transition into theouter wall die 240. The outer wall die 240 also has an outside die wall245 with an outside wall die aperture 246. A passage 223 in the mandrel220 provides air pressure to the inside of the pipe 10 at a point afterthe outer wall die 240 forms the outer wall 130 on the pipe 10. Aconnecting chain 225 secures a plug 224 inside the pipe 10 seals to themandrel 220 in order to maintain the pressure from the mandrel 220within the pipe 10.

[0044] Referring now to FIGS. 1, 2, and 3, in operation, a thermoplasticmaterial is extruded through the inner wall die aperture 211 onto theouter surface 221 of the mandrel 220 to form the inner wall 110 of thepipe 10. The outer surface of the mandrel 220 provides support to theinner wall 110 of the pipe 10 during the processes of applying thereinforcing textile 120 and the outer wall 130. After the inner wall 110has been extruded onto the mandrel 220, the reinforcing textile guide230 positions the reinforcing textile 120 onto the inner wall textileinterface zone 113.

[0045] Referring now referring to FIGS. 3 and 4A-H, the inside textileguide 231 and the outside textile guide 232 guide opposing ends of thereinforcing textile 120 as the reinforcing textile 120 is positionedonto the inner wall textile interface zone 113. FIGS. 4A-H illustratethe sequence of how the reinforcing textile guide 230 apply thereinforcing textile 120 onto the inner wall textile interface zone 113of the inner wall 110 in a sequential manner. The inside textile guide231 first applies one edge of the reinforcing textile 120 to the innerwall 110 of the pipe 10. As the inner wall 110 of the pipe 10 progressesalong the extruding apparatus 20, the outside textile guide 232continues to wrap the reinforcing textile 120 around the textileinterface zone 113 of the inner wall 110. In this manner, thereinforcing textile 120 surrounds the inner pipe 110 in a way thatreduces the possibility of wrinkles in the reinforcing textile 120 orair pockets between the inner wall 110 and the reinforcing textile 120.

[0046] Still referring to FIGS. 3 and 4A-H, in one embodiment a textilelocking system 123, in the form of ajoint material 123 a, is employedbetween the textile overlap sections 121 of the reinforcing textile 120to assist the reinforcing textile 120 to remain locked in an overlapposition when the finished pipe 10 is subjected to internal pressures.The joint material 123 a is injected between the textile overlapsections 121 by the joint material injector 235 just prior to theposition that the outside textile guide 232 joins together the textileoverlap sections 121. The joint material 123 a can be the same type ofmaterial that is used to form the inner wall 110, the outer wall 130, ora different material selected to help secure the textile overlapsections 121 from separating. In another embodiment, the joint material123 a is a tape, ribbon, strand, or the like that is placed intoposition between the textile overlap sections 121 prior to the textileguide 230 joining together the textile overlap sections 121.

[0047] In an alternative yet preferred embodiment, the textile lockingsystem 123 is a mechanical locking system utilizing mechanical devicessuch as hooks, piles, or other mechanical mechanisms. In a version ofthe textile locking system incorporating hook devices, a plurality ofhook devices extending up from the lower textile overlap section 121into the upper textile overlap section 121, down from the upper textileoverlap section 121 into the lower textile overlap system, or both. Thetextile locking system 123 using hook devices can use hook devicessimilar to the hook devices in a hook and pile closure system. In aversion of the textile locking system 123 that employs a pile typeelement, the pile type element can extend from the lower textile overlapsection 121 into the upper textile overlap section 121, from the uppertextile overlap section 121 into the lower textile overlap section 121,or both. The textile locking system 123 using a pile type element canhave a pile type element formed from the same fibers or yarns of thereinforcing material, and can also have the pile elements canted toangle back towards the center of the reinforcing textile 120. In anotherembodiment, the textile locking system 123 employing a mechanical devicecan incorporate the mechanical device onto a ribbon, strip, strand, orthe like that is placed into position between the textile overlapsections 121 prior to the textile guide 230 joining together the textileoverlap sections 121. The textile locking system 123 employing amechanical device in the form of a ribbon, strip, strand, or the like,the locking system 123 can also be positioned below the lower textileoverlap section 121 and extend up into both textile overlap sections121, or above the upper textile overlap section 121 and extend down intoboth textile overlap sections 121. Additionally the textile lockingsystem can employ both the joint material 123 a and the mechanicalsystems described above.

[0048] Referring back now to FIG. 3, once the textile locking system 123is located in place, the closing roller 237 presses the textile overlapsections 121 together in preparation for applying the outer wall 130.The outer wall 130 is formed around the inner wall 110 and reinforcingtextile 120 combination by the outer wall die 240. The inner wall 110and reinforcing textile 120 combination enters the outer wall die 240through the inside wall aperture 242 of the outer wall die 240. Theinside wall aperture taper 243 assists the inner wall 110 andreinforcing textile 120 combination transition into the outer wall die240. A thermoplastic material is extruded into the outer wall die 240and surrounds the inner wall 110 and reinforcing textile 120combination. The inner wall 110, reinforcing textile 120, and outer wall130 exit the outer wall die 240 through the outside die wall aperture246 in the outside die wall 245. The outside wall die 240 is illustratedin FIG. 3 as being perpendicular to the pipe 10; however, it iscontemplated that the outside wall die 240 can be at an angle such thatthe inside wall a inside die wall 241 and the outside die wall 245 forman acute angle to the inner wall 110 and reinforcing textile 120combination entering the outer wall die 240. This acute anglefacilitates the forming of the outer wall 130 on the pipe 10 and helpsreduce the tendency of the thermoplastic material to leak out of theinside die wall aperture 242.

[0049] Still referring to FIG. 3, air pressure applied to the passage223 in the mandrel 220 exits into the interior of the pipe 10 after theouter wall 130 has been formed. The plug 225 inside the pipe 10 helpsretain the pressure inside the pipe 10. A connecting chain 227 holds theplug 225 adjacent to the mandrel 220. The pressure applied within thepipe 10 prevents collapse of the entire structure as the three layerpipe 10 hardens into its final shape. After hardening, the plug 225 isremoved and the resulting pipe structure 10 is ready for utilization intandem with other such pipes (not illustrated) as an entire highpressure pipeline (not illustrated).

[0050] Referring now to FIG. 5, there is shown a partial view of atextile 300 for use as the reinforcing textile 110 illustrated in FIGS.1 and 2. The textile 300 includes electrode elements 311 and 312, andresistive elements 320. As illustrated in FIG. 5, the electrode elements311 and 312 are conductive materials that run parallel along the lengthof the textile 300 as the selvage yarns. The resistive elements 320 arewoven around the electrode elements 311 and 312, and interlaced to forma fabric. As an example, the resistive elements 320 can be a yarn formedof a flexible core having a fine resistance wire or tape wound spirallythereon, or having a layer of carbon particles bonded thereon by athermoplastic or resin binder. The electrode elements 311 and 312, andthe resistive elements 320 are flexible to form a fabric that can beplaced around the inner wall 110 as the reinforcing fabric 120illustrated in FIGS. 1 and 2.

[0051] Referring now to FIGS. 1-2 and 5, by using the textile 300 inFIG. 5 as the reinforcing fabric 120 in FIGS. 1 and 2, an electricalcurrent can be applied to the electrode elements 311 and 312 of thefabric 300 when in place within the pipe 10. The electrical currentsupplied to the electrode elements 311 and 312 passes through theresistive elements 320 and generates heat. In this manner, the pipe 10can be used to apply heat to the contents of the pipe 10, or tocompensate for the loss of thermal energy from the contents of the pipe10 to the exterior of the pipe.

[0052] Referring now to FIG. 6, there is shown another embodiment of atextile 400 for use as the reinforcing textile 120 of the pipe 10 inFIGS. 1 and 2. The fabric 400 generally comprises selvage yarns 430,electrode yarns 411 and 412, and resistive yarns 420. The electrodeyarns 411 and 412 are woven around the selvage yarns 430 such that aresistive yarn 420 separates each electrode yarn 411 and 412. At eachintersection of the electrode yarns 411 and 412, the electrode yarns 411and 412 are insulated from making an electrical connection to eachother. At each intersection of the resistive yarn 420 with one of theelectrode yarns 411 and 412, the resistive yarn 420 is placed inelectrical connection with the respective electrode yarn 411 or 412. Inthis manner, an electrical circuit is formed having the electrodes 411and 412 interconnected by a series of segments from the resistive yarn420, thus forming a parallel resistive circuit. The parallel resistivecircuit can generate heat in a similar manner to the textile 300 byapplying an electrical current between the electrode yarns 411 and 412.Additionally, any break in yam electrode 411 or 412, will create achange in the electrical potential across the electrode yarns 411 and412, indicating a location of the break. Therefore, a break within thepipe 10 causing a break of one of the electrodes 411 or 412, can belocated by measuring the electronic potential across the electrode yarns411 and 412.

[0053] In addition to the textiles 300 and 400 illustrated in FIGS. 5and 6, a traditional woven or knitted textile having thermal generatingelements can be incorporated as the reinforcing textile 120 illustratedin FIGS. 1 and 2. For example, a traditional woven fabric having selvageyarns, pick yarns, and filling yarns, can incorporate the thermalheating aspects of the textiles 300 and 400. The picks of a traditionalwoven fabric can be the resistive elements, and the selvage yards and/orfill yarns can be a conductive material. Alternatively, the fill yarnscan be formed of a resistive material, and the pick yarns can beconductive yarns which are electrically supplied by conductive selvageyarns and/or conductive fill yarns. In yet another embodiment, theresistive yarns can be a combination of pick and fill yarns.

[0054] Referring now to FIG. 7, there is shown an apparatus 500 for thein situ formation and placement of an embodiment of the pipe from thepresent invention. The apparatus 500 includes a transportation device510 such as a truck, a trench or ditch digging device 520 located on thetransport device 510, and an apparatus for formation of the pipe 530such as the pipe forming apparatus 20 in FIG. 3. A supply of reinforcingtextile 540 (such as a roll of the reinforcing textile 120 in FIG. 1) ispositioned with the transportation device 510 to supply the pipe formingdevice 530 with the necessary reinforcing material 120 to form the pipe10. Additionally, an extruding device 550 with a plastic supply 551 ispositioned with the transportation device 510 for supplying meltedmaterial to the inner wall dye 210 of the pipe forming apparatus 200 forforming the inner wall 110 of the pipe 10. A second extruding device 560with a material supply 561 extrudes material and supplies the materialto the outer wall die 240 of the pipe forming apparatus 530 for formingthe outer wall 130 of the pipe 10. Although the two extruding devices550 and 560 have been illustrated as a separate supply, it iscontemplated that the two extruding devices could be a single extrudingdevice.

[0055] Still referring to FIG. 7, the ditch or trench digging device 510removes material from the ground for placement of the pipe 10. Theextruding apparatus 520 receives extruded material from the extrusiondevice 550, reinforcing material 20 from the supply, and extrudedmaterial from the extrusion device 560 for forming the inner wall 110,reinforcing textile 120, and outer wall 130, respectively, of the pipe10. The pipe 10 is positioned within the trench or ditch formed by thetrench or ditch digging device 520 and earth is placed over the pipe 10as necessary. The process is continuous allowing the transportationdevice 510 to form and place the pipe 10 in situ.

[0056]FIG. 8 thus shows four separate textile reinforcement materials610, 620, 630, 640, each with individually tapered ends 612, 614, 622,624, 632, 634, 642, 644, that have been arranged around thecircumference of the target resin pipe 602. Upon contacting of thesematerials 610, 620, 630, 640, as shown, the tapered ends 612, 614, 622,624, 632, 634, 642, 644, overlap with each other and, upon introductionof molten resin which then cools, the reinforcement materials 610, 620,630, 640 thus adhere not only together, but also with the resinmaterials 602, thereby providing a reinforced pipe 602.

[0057]FIG. 9 shows one preferred embodiment of an inventive molding dorn700. The end shown 702 comprises a plurality of similarly shapedindentations 704 which thus creates a very large surface area thereon.FIG. 10 shows the other end 706 of the same preferred inventive moldingdom 700 of FIG. 9. The diameter thereof of the second end 706 is thesame as that measured to the greatest extension of the indentations 704of the first end 702. FIG. 11 thus shows the same preferred inventivemolding dorn 700 of FIGS. 9 and 10, depicting the modification ofsurface area (through indentations 704) of the dorn 700. The number andamount of indentations 704 is gradually and continually reduced as oneviews the dorn from the first end 702 to the second end 706. In order tokeep the dom 700 in place during pipe production, any method can beemployed including adhesion, magnetism, and the like. As shown in FIGS.12 and 13, it is thereby easier for the resin components 708 to adhereto one another, or alternatively, for such resin components to becomemore thoroughly adhered thereto during molding to the textilereinforcement materials 710 by permitting the forcing through of theresin components 708 over the entire length of the dorn 700 during themolding step. As the first end 702 is of greater surface area than theother areas of the dorn 700, and particularly the second end 706, whichis round in shape to produce the ultimately desired round shape of thepipe article. Pressure is applied to the resin components 708 andtextile reinforcement materials 710 by a wider extrusion device (ormandrel 520 in FIG. 7). The pressure thus exerted presses the resincomponents 708 and reinforcement materials 710 to the dorn 700 duringextrusion. The first end (702 of FIG. 9) is preferably heated to atemperature permitting the resin components 708 to be in molten stateinitially. After extrusion over the molding dorn 700, then, the moldedpipe article is permitted to cool into its molded shape.

[0058] The inventive molding dorn may also exhibit or possessalternative or extra indentations or patterns for other benefits aswell. For example, small corrugated patterns transferred from themolding dorn to the ultimate inner surface of the subject pipe can aidin reducing friction within the pipe itself if such pipes are utilizedfor the containment of cables (fiber optics, for example). Since suchcables must be pulled through or pushed through the entire pipe systemto effectuate such containment, and such introduction is performed athigh rates of speed, the need to potentially reduce the friction on theintroduced cables (to reduce the chances of wearing of the cablesthemselves, for example) is noticeable. The modification of the moldingdorn to provide such a corrugated pattern (or like alternative patternfor the same effect) is thus contemplated as at least one alternative inthis invention.

[0059] Having described the invention in detail it is obvious that oneskilled in the art will be able to make variations and modificationsthereto without departing from the scope of the present invention.Accordingly, the scope of the present invention should be determinedonly by the claims appended hereto.

What is claimed is:
 1. A method of producing a resinous pipe comprisingat least one layer of thermally manipulated polymeric material, whereinsaid polymeric material is first heated and applied around a first endof a molding dom having a first end and a second end as well as areas inbetween, and subsequently moved along the length of said dom to saidsecond end of said dom and eventually cooled, wherein said dorn exhibitsthe shape diameter throughout its entire structure, but exhibits agreater surface area at said first end than at said second end.
 2. Themethod of claim 1 wherein said dorn exhibits a reduction in surface areanumerically from said first end through all areas in between said firstend to second end and ultimately to said second end.
 3. The method ofclaim 2 wherein said dorn is substantially round in shape at said secondend.
 4. The method of claim 1 wherein said resinous pipe comprises areinforcement material.
 5. The method of claim 4 wherein saidreinforcement material comprises at least two different componentsadhered to said resinous material.
 6. The method of claim 3 wherein saidreinforcement material is a textile material.
 7. The method of claim 4wherein said reinforcement material is a textile material.
 8. A moldingdorn comprising a first end and a second end with areas in between saidfirst and said second end, wherein said dorn exhibits the same diameterover its entire length and wherein said dorn exhibits a reduction insurface area numerically from said first end consecutively through allareas in between said first end to second end and ultimately to saidsecond end.
 9. The molding dorn of claim 8 wherein said dorn issubstantially round at said second end.